The present invention relates to a dry powder inhaler for administration of a medical dry powder to the lungs of a user, and more exactly to an airbrake device for prolonging the time for dose delivery upon inhalation.
Today supply and distribution of medical powders take place in many different ways. Within health care more and more is focussed on the possibility to dose and distribute powder directly to the lungs of a user by means of an inhaler to obtain an efficient, fast, and user friendly administration of the specific medical substance.
Inhalers have been developed from being very simple to the up-to-date relatively complicated devices. For the up-to-date inhalers some form of dosing process is almost entirely used for preparing the dose to be inhaled. Most often the dosing of the amount to be inhaled takes place industrially in advance in a dose package containing of the order 5-50 doses. The inhaler then is loaded with this dose package as the source of each dose. Other inhalers have a magazine from which the powder is dosed by some device for distribution to the inspiration air. In both cases the powder will generally be strongly agglomerated and therefore must be dispersed.
This dispersion of the agglomerates today mainly takes place by means of techniques in which the energy of the inspiration air is utilized. A normal inhalation takes place during about two seconds and a peaceful inspiration takes 3-4 seconds. In such designs, in which only the inhalation air is utilized for the de-agglomeration, only a fraction of the energy of the inhalation air will be utilized, as the dose of powder is given normally during only 0.1 to 0.4 s. Consequently this results in a low exploitation of the available energy which, as a matter of fact, will be present in the inhalation air. As only a small portion of the amount of energy is used it will be too low for a sufficient de-agglomeration to take place. The total respirable dose therefore becomes very dependent on the occasion and the individual user and thereby very varying from time to time. To improve this condition a number of inhalers include some kind of device against which the powder should collide and thereby transfer energy for de-agglomerating the powder. However, such a collision with a fixed or mechanically moving object involves that a relatively large amount of powder sticks either permanently or is transported further together with the next dose. In both cases this constitutes a negative factor for the goal of obtaining a high accuracy and quality of the inhaled dose, e.g. an accurate amount of powder having a high portion of very small particles.
In a document WO97/00704 is described an inhaler device in which the substance to be administered is charged electrostatically and the dosing is performed by means of the assistance of a rotating dosing drum attracting the charged particles of the substance. The substance is then emitted from the dosing drum by means of a combination of an additional electric field and the air stream resulting from an inspiration. In advance of a desired dosing step the substance to be administered is kept in a reservoir, loaded for instance by means of receiving a cartridge containing the substance intended for many operations of the device.
However here is still a demand for simple means for prolonging a dose delivery during an inhalation to obtain a full effectiveness of a pre-metered medical powder dose administered to a user""s lung.
The present invention discloses a device for controlling the duration of an administration of a prescribed dose of dry powder to a user""s lung when inhaling the powder by means of a dry powder inhaler (DPI). The present device controls the speed and time characteristics of a moving cassette carrying medical powder doses to one by one be administered by the DPI to a user. Generally the dose is pre-metered and applied to the cassette in the form of a strip or a series of spots of ready-prepared powder. An airbrake device prolongs the time during which the pre-metered powder dose is released to the inhalation air. Adjustment means of the airbrake device define the motion speed of a motion of spring-loaded cassette during which the powder dose is sucked from the prepared dose powder strip onto the cassette by a nozzle connected to a mouthpiece.
A device for controlling dosing speed and timing of an inhaler device is set forth by the independent claim 1, and further embodiments are set forth by the dependent claims 2 to 7.